The present proposal is based on the hypothesis that androgen induces cellular responses via the activation of both gene expression and kinase cascade. The former is widely recognized, since the receptor for androgen itself is a transcriptional factor. The latter has begun to be appreciated in recent years, largely due to the realization that phosphorylation is an integral part for virtually all cellular processes. These two mechanisms however are not mutually exclusive, as transcriptional activation can lead to upregulation of kinases or phosphatases, thereby directly influencing the phosphorylatiion signaling. The present proposal is concerned with a novel serine kinase that is transcriptionally activated by androgen and that in turn regulates androgen receptor activity. It is generally overexpressed in prostate cancer cells, compared to normal counterpart. It is male-cell speciic and appears to be an integrator of signals coming from androgen and growth factor. There are three specific aims of the proposal: 1. To characterize MAK as a target of androgen activation. 1. To characterize MAK as a regulator of androgen receptor. 1. To characterize MAK as a modulator of androgen prostate cancer growth.